New features

• Add #{|input, pos| ... } custom expr (#395)
• Allow type bounds (e.g. Box<dyn Operand + 'input>) in rule return types (#385)
• Allow specifying generic arguments (e.g. my_rule::<u32>()) when calling a rule. (#396)

Deprecations

The never-documented ##method() syntax is deprecated because the ## token is not allowed by Rust edition 2024. It will be removed in rust-peg v0.9. ##method() can be replaced with #{|input, pos| input.method(pos) }.

Contributors

@kevinmehall @brasswood

Full Changelog: 0.8.4...0.8.5

Fixes

• Fix error with [x..] range pattern (1b2da45)

Improvements

• Allow inlining standard Parse trait impls by @neocturne (#374)
• Support where clauses on rules by @A4-Tacks (#371)
• Support trailing commas in type parameter lists by @A4-Tacks (#371)
• Improve compatibility with Rust qualified path syntax in type grammar by @A4-Tacks (#371)

Other

• Remove support for crate visibility modifier, which was dropped from rustc nightly in 2022

• Allow expected!() to accept a &'static str expression, not just a literal. (#361)
• Use BTreeSet in ExpectedSet for deterministic ordering. (#336)
• Add enabled-by-default std feature that can be disabled to build on no-std + alloc (#336)
• Fix regression with impl Trait return types (#319)

Contributors

@stevefan1999-personal @Flamenco @tchajed @kevinmehall

Fixes

• Fix type inference for generic argument in rule's return position (#317)
• Fix parsing of &'a mut T in type grammar (#304)

Improvements

• Made LineCol Copy (#298)

Contributors

@kevinmehall @plaflamme @zsol @Kile-Asmussen @kw217

New Features

• #[cache_left_rec] annotation to allow left recursion (#266)
• Return matched token/character from [ ] pattern expression (#234)

Fixes

• Fix Rust grammar for arguments (#261) and type bounds (#279)
• Fix trace feature when using infix!{} (#277)
• Fix #[cache] with grammar lifetime parameters
• Allow clippy::redundant_closure_call lint in generated grammar (#258)

Breaking changes

Most users will not require changes to upgrade from 0.7 to 0.8; these only affect advanced use cases.

• Allow only lifetime, not type, parameters at the grammar level. (type parameters were never properly supported)
• Add 'input lifetime parameter to ParseElem trait so implementations can return tokens by reference. (#268)
• Require Copy on ParseElem::Element to better represent the expectation that they are cheap to copy/move.

---

Contributors: @kevinmehall @zsol @neunenak @fgasperij

New features

• Significantly improved compile-time error messages for invalid grammars
• Support [MyToken(x)] syntax for capturing variables from pattern expressions (#245)
• Restore support for [^ ] inverted pattern syntax
• Add #[no_eof] pub rule() = ... syntax to allow matching a prefix of the input rather than reporting a parse error if the rule does not reach end-of-file (#233)
• Allow rule _ = without parentheses when defining special underscore rule (#243)
• Add grammar-level type and lifetime parameters (#254)
• Compile-time check for repeat expressions that infinite-loop without consuming input (#210)
• Implement PartialEq, PartialOrd, Eq, Ord, Debug, Hash for RuleResult (#217)

Fixes

• Extend detection of infinite-loop left recursion to check inside precedence!() (#238)
• Wrap user-supplied code in immediately-invoked closure so that return and ? behave as expected (#246)
• Remove overzealous error checks to allow passing rule closure arguments as parameters to another call (#226)

Breaking changes

• Add required is_eof() method to Parse trait (#252)
• Certain patterns that would infinite-loop or stack overflow if executed are now a compile-time error
• mixed_site hygiene prevents action code from accessing internal parser state variables such as __input, __pos, etc.

Contributors

@kevinmehall @dario23 @bgw @adrianwn

• Fix multiline doc-comments (#232)
• Documentation improvements

Contributors: @dario23 @kevinmehall

• Derive PartialEq, PartialOrd, Eq, Ord, Debug, Hash for RuleResult (#217)
• Documentation improvements

Contributors: @dario23 @kevinmehall